Cleanup packages/Tethering/common/TetheringLib

Merge the otherwise unused tethering-aidl-interfaces into
framework-tethering.

This is in preparation for converting to use java_sdk_library.

Bug: 155164730
Test: m droid
Merged-In: I4583539d11ba69320aa5a0dfcfee072c81affac2
Change-Id: I4583539d11ba69320aa5a0dfcfee072c81affac2
(cherry picked from commit 267dd95c)